This invention relates to a device for measuring the oscillations of an oscillating support for the shaft of a rotor, upon which a rotor to be balanced in a balancing machine is mounted. The balancing machine measures the amount of imbalance of the rotor in two planes.
The device comprises two pairs of two parallel bar springs, each spring of a pair mounted in the same direction in which the axis of the rotor extends and at a distance from the other spring of the pair. The springs support a rotor shaft housing on a machine stand in such a way that they oscillate within a plane of oscillation that contains the axis of the rotor. During dynamic balancing, the imbalance of a rotor is measured in two separate planes that are parallel to the axis of the rotor, and to which devices picking up the measuring values have been assigned. In order to accurately ascertain the amount of imbalance, it is necessary to separate the imbalance measurement in one plane from the imbalance measurement in the other plane. Any effects of one plane acting on the other plane have to be suppressed.
Disadvantageous effects on measured results have been known to arise in devices of this sort, especially from fastening sites on the ends of the springs. The difficulty is due to the fact that the fastening sites on the end of each spring may be below the rigidity of the spring. The path of oscillation caused by the imbalance of the revolving rotor is thereby partly determined by the rigidity of the spring connection at each spring end. Modifications of the connections affect the amplitudes and the phase relationships of the oscillatory movements. This causes difficulties in the separation of the planes in which measuring takes place. In addition, even small manufacturing defects at the sites of fastening of the springs bring about considerable stresses in the oscillating spring system.
Accordingly, it is a primary object of the invention to create a device of the type mentioned at the outset, and in which an exactly defined spring setting is achieved at the fastening sites of the spring ends connecting the machine stand with the rotor shaft housing or mounting.